RCCPAC: A parallel relativistic coupled-cluster program for closed-shell and one-valence atoms and ions in FORTRAN

TL;DR

This paper introduces RCCPAC, a parallel FORTRAN program that efficiently solves relativistic coupled-cluster equations for atoms and ions, enabling accurate property calculations on distributed memory systems.

Contribution

The paper presents a novel parallel FORTRAN implementation of relativistic coupled-cluster equations using message passing interface for atoms and ions.

Findings

Successfully computes ground state correlation energies

Calculates attachment energies and hyperfine constants

Demonstrates scalability on distributed systems

Abstract

We report the development of a parallel FORTRAN code, RCCPAC, to solve the relativistic coupled-cluster equations for closed-shell and one-valence atoms and ions. The parallelization is implemented through the use of message passing interface, which is suitable for distributed memory computers. The coupled-cluster equations are defined in terms of the reduced matrix elements, and solved iteratively using Jacobi method. The ground and excited states coupled-cluster wave functions obtained from the code could be used to compute different properties of closed-shell and one-valence atom or ion. As an example we compute the ground state correlation energy, attachment energies, $E$1 reduced matrix elements and hyperfine structure constants.